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Multimeter CAT II Rating Discontinuation
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Fungus:

--- Quote from: bdunham7 on July 25, 2023, 11:38:15 pm ---But I'm a bit doubtful that they would be that flawed or that Fluke would deliberately (or even negligently) publish false information that clearly contradicts what you are claiming is the standard.  My best guess, based only on speculation and language from Fluke's reference, is that there is additional language specifying a single-phase receptacle/plug, not just any receptacle/plug.

--- End quote ---

To me that "10m from CAT III" seems like a very specific thing, something that Fluke wouldn't invent if it wasn't in the standard. That document has been around for many years and it makes perfect sense that the danger from transients diminishes gradually with distance, not in sudden steps. I'll need a lot of convincing that Fluke is wrong and a random forum poster is right.


--- Quote from: bdunham7 on July 25, 2023, 11:38:15 pm ---If the 'standard' here is just 'guidance' that provides rules of thumb and expects you to fill in the rest with common sense, than IMO that's not much of a standard.

--- End quote ---

Yep.
joeqsmith:

--- Quote from: Fungus on July 26, 2023, 07:42:49 am ---... makes perfect sense that the danger from transients diminishes gradually with distance, not in sudden steps. I'll need a lot of convincing that Fluke is wrong and a random forum poster is right.   ...

--- End quote ---

Not just incoming transients.  Fault current goes up.  Think about the idiots that try and measure the AC current by placing the meter in current mode across the mains.   I took some measurements a while back in my home for someone showing how the distance effects it.    Also measured some larger outlets at work for fun.   

Still a big difference between the kid plugging sissors into the home wall socket and the service tech arching a 480 bus.   
Someone:

--- Quote from: joeqsmith on July 26, 2023, 05:56:50 pm ---
--- Quote from: Fungus on July 26, 2023, 07:42:49 am ---... makes perfect sense that the danger from transients diminishes gradually with distance, not in sudden steps. I'll need a lot of convincing that Fluke is wrong and a random forum poster is right.   ...
--- End quote ---
Not just incoming transients.  Fault current goes up.  Think about the idiots that try and measure the AC current by placing the meter in current mode across the mains.   I took some measurements a while back in my home for someone showing how the distance effects it.    Also measured some larger outlets at work for fun.   

Still a big difference between the kid plugging sissors into the home wall socket and the service tech arching a 480 bus.
--- End quote ---
Yes, the real world is highly variable. Fluke presents some suggestions of what they think are appropriate conditions given the specific ratings of their meters, but that is not supported by or in the standard, just some practical advice from a manufacturer. Would I rely on that advice to cover my liabilities? No.
bdunham7:

--- Quote from: Someone on July 26, 2023, 01:28:47 am ---Yes, the delineations are not perfect but there is no perfect delineation as the world is complex.

--- End quote ---

OK, but I think the much smaller point I'm trying to make is that the delineation could be much better (not perfect) by simply adding the language "single phase receptacle".  Fluke has somehow read in or added this specific language but perhaps they've just added their own common sense take to the standard...I don't know.  And the IEC appears to be moving in the right direction, IMO. 


--- Quote ---Why is it so hard for people to understand????

--- End quote ---

Because it doesn't make intuitive sense and results in absurd results in certain very plausible situations like the case I proposed.


--- Quote ---Otherwise you end up with an impossible to meet standard that covers a soaking wet gorilla probing a socket outlet outside in the rain, which is connected back to the poles with some obscure 120mm2 cable, during lighting strike on the nearest pole.... and the meter needs to continue operating perfectly afterwards despite being on current mode and connected across the phases.

--- End quote ---

My contrived example was based on things that I've either seen and handled myself or that I'm actually sure exist and are reasonably common.  I understand the need for some simplicity and that they don't want to require a complete fault current analysis signed off by a PE before anyone can ever connect a meter to anything.  That doesn't mean there isn't room for improvement and if what you insist about the standard is correct, there's some pretty low hanging fruit there IMO.
bdunham7:

--- Quote from: tautech on July 26, 2023, 12:35:31 am ---How much need a manufacturer hold the hand of their users ?  :-//

--- End quote ---

I think they should do the easy, common sense things that make it possible for a someone with experience with similar equipment, but not identical, to use its basic functions without reading the manual.  Now if we're talking HF AC, then I don't expect them to have a pull-out chart to guide me through that.   



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